JPS635812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording/reproducing device (video tape recorder: hereinafter abbreviated as VTR), and particularly to a VTR improved to effectively compensate for tracking deviations.

As is well known, VTRs are used to record video signals on magnetic tape or to reproduce video signals recorded on magnetic tape.

Figure 1A shows the video recording section of a conventional VTR.
FIG. 1B is a diagram schematically showing a magnetic tape on which a video signal is recorded by a conventional video recording section. The video recording section 10 includes a head drum 11. The head drum 11 has a head (first head) 12 for recording or reproducing video signals.
and 13 is a certain angle on its circumference (in the illustration
180 degrees) apart. A magnetic tape 1, which is wound around a supply reel 14 and transferred to a take-up reel 15, is wound obliquely around the head drum 11. That is, the head drum 11 is rotatably provided at a position where the magnetic tape 1 runs.
Between the head drum 11 and the take-up reel 15,
A capstan 16 and a pinch roller 17 are provided across the magnetic tape 1.

By the way, when the VTR is of the VHS format, the positional relationship between the length direction of the magnetic tape 1 and the head drum 11 is such that the right side is downward and the left side is upward. Therefore, the magnetic pattern of the video signal recorded on the magnetic tape 1 is as shown in FIG. 1B. Also,
In the VHS system, the recorded A track 2 is recorded at an azimuth of 6 degrees, and the currently recorded B track 3 is recorded at an azimuth of -6 degrees. Note that x in the figure indicates the running direction of the magnetic tape 1, and y indicates the running direction of the head.

FIG. 2 is a circuit diagram of a VTR which is the background of this invention. In the configuration, the background VTR includes a recording system block 21, a head selection switch 22, a rotary transformer 23, a reproduction system block 24, a tape drive circuit 25, a mode selection switch 26,
Track identification signal supply circuit 27, filter 281
283 and control circuit 29.

Here, the recording system block 21 includes the video signal source 2
11, luminance signal passing filter 212, color signal passing filter 213, FM demodulator 214, addition circuit 2
15 and a low frequency converter 216. The reproduction system block 24 includes head amplifiers 241 and 242,
Adding circuit 243, FM video signal passing filter 24
4, includes an FM demodulator 245, a low frequency color signal passing filter 246, a high frequency converter 247, an adder circuit 248, and an output terminal 249.

The mode selection switch 26 includes a recording command switch 261, a reproduction command switch 262, a stop command switch 263, a high speed reproduction command switch 264, and a temporary stop command switch 265.

The track identification signal supply circuit 27 includes a plurality of signal sources 271 to 273 and a changeover switch 274, which is an example of a changeover means. The signal sources 271 to 273 are
Each has a frequency band that does not adversely affect the video signal, and each has a different frequency selected. The filters 281 to 283 are connected to the signal source 271
.about.273, respectively, and are band pass filters that pass track identification signals in frequency bands generated by the corresponding signal sources.

Next, with reference to FIGS. 1A, 1B, and 2, the operation of a VTR, which is the background of the present invention, will be explained.

First, signal processing in recording mode will be explained. In the recording mode, each switch 221, 222 included in the head changeover switch 22 is switched to the upper side (R contact side). In this state, the video signal generated from the video signal generation source 211 consists of a luminance signal of up to about 3 MHz and a chrominance signal of 3.58 MHz. This luminance signal passes through a luminance signal passing filter 212 and is applied to an FM modulator 214. The FM modulator 214 has a luminance signal of 3.4M
Addition circuit 21 modulates from Hz to 4.4MHz FM signal
Give to 5. On the other hand, the color signal passes through a color signal passing filter 213 and is applied to a low frequency converter 216. The low-pass converter 216 converts the color signal into a 629kHz signal and supplies it to the addition circuit 215. The addition circuit 215 adds the FM-modulated luminance signal and the low-frequency converted color signal. This addition signal (that is, the frequency-modulated video signal) is given to the head 13 via a switch 211 included in the head changeover switch 22 and a transformer 231 included in the rotary transformer 23, and is also given to the head 13 via a switch 222 and a transformer 232. Head 1
given to 2. The head 12 is the head drum 1
A modulated video signal (including a luminance signal and a chrominance signal) is recorded on the A track 2 during the period in which the A track 1 rotates for half a rotation. The head 13 records the modulated video signal on the B track.

Next, signal processing in playback mode will be explained. In this case, the reproduction command switch 262 is pressed. In response, the tape running drive circuit 25 moves the switches 221 and 222 to the lower side (P contact side).
Switch to In this state, A of the magnetic tape 1
The recording signal (i.e. video signal) recorded on track 2 is selected by the azimuth and sent to head 1.
2, transformer 232 and switch 2
22 to a head amplifier 242.
The head amplifier 242 amplifies the reproduced signal and supplies it to the adder circuit 243. Similarly, the recording signal recorded on the B track 3 of the magnetic tape 1 is transferred to the head 1.
3 and applied to the head amplifier 241 via the transformer 231 and switch 221. The head amplifier 241 amplifies the reproduced signal and supplies it to the adder circuit 243. The adder circuit 243 adds the reproduced signals of both A track 2 and B track 3, and passes the signals to the FM video signal passing filter 224, the low frequency color signal passing filter 246, and the filter 28.
1 to 283. The FM video signal passing filter 244 passes the FM video signal in the frequency band modulated by the FM modulator 214 and outputs the FM video signal to the FM demodulator 2.
Give to 45. FM demodulator 245 demodulates the FM video signal to derive a luminance signal and supplies it to adder circuit 248 . On the other hand, the low-pass color signal passing filter 246 passes the low-pass color signal converted by the low-pass converter 216 and supplies it to the high-pass converter 247 .
The high frequency converter 247 converts the low frequency color signal into a 3.58 MHz color signal and supplies it to the adding circuit 248. Adding circuit 248 adds the demodulated luminance signal and color signal and outputs the result to output terminal 249 as a video signal.

Next, the case of recording track identification information will be explained. Recently, with the trend toward high-density recording with track widths of 19 μm, it is required that the head accurately trace during playback. As a concrete means of achieving this, identification signals of different frequencies are recorded on adjacent tracks, and during playback, the track identification signal of the adjacent track is minimized, or the identification signal of the reproduced track is maximized. Another technique is to change the relative position between the magnetic tape and the head.

For example, signal source 271 generates a 1 MHz track identification signal, signal source 272 generates a 1.2 MHz track identification signal, and signal source 273 generates a 1.4 MHz track identification signal.
track identification signal.
When recording on the magnetic tape 1, the changeover switch 274 sequentially and cyclically switches the signal sources 271, 272, and 273 to each signal source 271 to 273.
Track identification signals of different frequencies from the output of 273 are sequentially and repeatedly selected and applied to adder circuit 215. As a result, the track identification signal is recorded on each track of the magnetic tape 1 in synchronization with the recording of the video signal.

In the playback mode, the head amplifier 241,
242, a 1 MHz track identification signal is extracted by a filter 281 and given to the control circuit 29. A 1.2 MHz identification signal is extracted by filter 282 and provided to control circuit 29 .
Furthermore, the 1.4MHz track identification signal is passed through filter 2.
83 and provided to the control circuit 29. The control circuit 29 determines the magnitude relationship of the amplitude (or voltage value) of each frequency of the track identification signal, detects the relative positional relationship of the head 12 or 13 with respect to the magnetic tape, and performs a predetermined operation based on the detection result. The tape running speed of the tape running drive circuit 25 is controlled so that tracking is performed.

For example, a 1.2 MHz track identification signal is recorded on track 2, a 1 MHz track identification signal is recorded on track 3', which was recorded immediately before track 2, and a 1.2 MHz track identification signal is recorded on track 3, which follows track 2.
Let us assume that a 1.4MHz track identification signal is recorded. In this case, the head 12
When the player is playing track 2, the 1.2MHz track identification signal amplitude is at its maximum. However, when the running speed of the magnetic tape 1 slows down and the head 12 straddles the track 3', the 1 MHz track identification signal increases. In this case, the control circuit 29 is 1M
The tape drive circuit 25 is controlled to increase the rotational speed of the capstan 16 as the Hz rotor track identification signal increases. This allows the head to track a predetermined track.

Conversely, if the head 12 straddles the track 3, the rotational speed of the capstan 16 may be reduced.

However, the circuit shown in Figure 2 has the problem that the track identification signal interferes with the sideband of the color signal, disturbing the color, and also interferes with the sideband of the FM modulation signal, disturbing the brightness. occurs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic recording and reproducing apparatus that can reduce interference with video signals even when track identification signals are recorded.

In summary, the present invention prevents the track identification signal from interfering with the video signal by recording the track identification signal with a head having an azimuth different from the head for recording the video signal. It is designed to reduce the

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 3A is an illustrative diagram of a video recording unit included in a VTR according to an embodiment of the present invention, and FIG. 3B is a diagram illustrating a recording state of a magnetic tape recorded by the video recording unit of this embodiment. FIG. The video recording section 10A of this embodiment differs from the video recording section 10 of FIG. 1A in that the head drum 11 is constructed as follows. That is, in this embodiment, the first head 1 used for recording or reproducing video signals
In addition to 2 and 13, second heads 18a and 18b
is provided. The second head 18a has a different azimuth (e.g. +30°) than the first head 12.
It is attached to the head drum 11 so that The second head 18b is mounted on the head drum 11 so as to have a different azimuth than the first head 12 (for example, -30 degrees). This second head 18
a and 18b are selected to be slightly forward in the rotational direction from the mounting angle of the first heads 12 and 13. Then, before the first heads 12 and 13 record the video signal, the second heads 18a and 1
8b records a track identification signal, and during reproduction, the second heads 18a, 18b reproduce the track identification signal before the first heads 12, 13 reproduce the video signal.

FIG. 4 is a circuit diagram of a VTR according to an embodiment of the present invention. The VTR of this embodiment differs from the circuit of FIG. 2 in that in addition to the second heads 18a and 18b, transformers 233 and 234, switches 223,
224, head amplifiers 31 and 32, and an adder circuit 33. In this embodiment, the second heads 18a, 18b record or reproduce the track identification signal, and provide the reproduced track identification signal to the filters 281-283. The rest of the configuration is the same as that in FIG. 2, so the same parts are indicated by the same reference numerals and detailed explanation thereof will be omitted.

Next, the specific operation of this embodiment will be described with reference to FIGS. 3A, 3B, and 4. First, the operation in recording mode will be explained. in this case,
In response to the operation of the recording command switch 261, the switches 221 to 224 are switched to the upper side (R contact side). And recording block 2
A video signal FM modulated by 1 is applied to first heads 12 and 13. Now, the first head 1
3 records a video signal on track 3', selector switch 274 selects signal source 271 and supplies it to second head 18b via switch 224 and transformer 234. For this reason,
A 1MHz track identification signal and a video signal are overwritten on track 3'.

Then, the head drum 11 rotates half a rotation, and the first
Immediately before the head 12 starts recording the video signal on the next track 2, the selector switch 274 switches the signal source 2.
72. Therefore, the 1.2MHz track identification signal output from the signal source 272 is transmitted to the switch 2.
23 and transformer 233 to the second head 18a and recorded on track 2.
Therefore, the 1.2 MHz track identification signal and the video signal are overwritten on track 2.

Immediately before starting recording of the video signal on the next track 3, the changeover switch 274 is switched to the signal source 273. Therefore, the output of the signal source 273
A 1.4 MHz track identification signal is transmitted to the second head 18b via switch 224 and transformer 234.
given to. Therefore, a 1.4 MHz track identification signal is recorded on track 3. Truck 3
A video signal is superimposed thereon by the first head 13.

Thereafter, in the same way, the changeover switch 274 is sequentially and cyclically changed every time the track on which the video signal is to be recorded is changed. Therefore, track identification signals of different frequencies are recorded on each track of the magnetic tape 1 between adjacent tracks.

Note that even if a track identification signal is recorded in addition to a video signal on each track, the frequency bands of the video signal and the track identification signal are different, and the azimuths of the first head and the second head are selected so that they are different. This has the advantage of preventing adverse effects during playback.

Next, the operation in playback mode will be explained. In the case of reproduction mode, reproduction command switch 262 is pressed. Therefore, the tape running drive circuit 25 switches the switches 221 to 224 to the lower side (P contact side). In this case, the second head 18a or 18b
The track identification signal reproduced by
4 to head amplifiers 31 and 32. This track identification signal is applied to filters 281-283 via adder circuit 33. Each of the filters 281 to 283 passes the track identification signal in the frequency band corresponding to the signal sources 271 to 273, and provides its output to the control circuit 29. The control circuit 29 controls which filters 281 to 28
It is determined whether the amplitude (or voltage value) of the signal given from 3 is the largest, and depending on the magnitude, it acts on the tape running drive circuit 25 to change the running speed of the magnetic tape 1. The method of changing the running speed of the magnetic tape 1 in this case is the same as in the case of FIG.

The feature of this embodiment is that the second head 18a, 1
8b, before reproducing the video signal in the first heads 12 and 13, it reproduces a track identification signal recorded in advance at a different frequency for each adjacent track, and then reproduces the track identification signal at a frequency corresponding to the track being reproduced. The running speed of the magnetic tape 1 is changed so that the recorded track identification signal becomes the largest. This has the advantage of always being able to accurately compensate for tracking deviations. Further, since the azimuths of the first head and the second head are different, there is an advantage that even when a track identification signal is recorded, it is possible to prevent an adverse effect on the video signal.

Incidentally, in the above-described embodiment, the case has been described in which the running speed of the tape, that is, the rotational speed of the capstan is changed as a means for changing the relative positional relationship between the magnetic tape 1 and the first and second heads.
However, in order to change the relative position of the two, it can be achieved not only by this but also by other means.
For example, heads 12 and 18a may be attached to the same piezoelectric body and heads 13 and 18b may be attached to the same voltage body so that the two piezoelectric bodies can be moved up and down. In that case, the amount of vertical movement of the piezoelectric body is controlled by the output of the control circuit 29.

As described above, according to the present invention, since the video signal is recorded (overwritten) after the track identification signal is recorded, the recording magnetization level of the video signal is higher than that of the conventional track identification signal. , and due to the azimuth effect, the first
The track identification signal is hardly reproduced in the head, and the unique effects include that the interference to the color and luminance signals can be significantly reduced, the interference to the reproduced signal can also be reduced, and the noise during reproduction can be reduced.

[Brief explanation of the drawing]

FIG. 1A is an illustrative diagram of a video recording section of a conventional VTR, and FIG. 1B is a diagram illustrating a state in which video is recorded on a magnetic tape using the video recording section. FIG. 2 is a circuit diagram of a VTR which is the background of this invention. FIG. 3A is an illustrative diagram of a video recording section included in a VTR according to an embodiment of the present invention, and FIG. 3B is a diagram illustrating a state in which video is recorded on a magnetic tape using the video recording section. Figure 4 shows a VTR of one embodiment of this invention.
FIG. In the figure, 1 is a magnetic tape, 10 and 10A are video recording units, 11 is a head drum, 12 and 13 are first heads, 14 is a supply reel, 15 is a take-up reel, 18a and 18b are second heads, and 21 is the recording system block, 22 is the head changeover switch, 23
is a rotary transformer, 24 is a reproduction system block, 2
5 is a tape running drive circuit, 26 is a mode selection switch, 27 is a track identification signal supply circuit, 281
~283 is a filter, 29 is a control circuit, 31,3
2 represents a head amplifier, and 33 represents an adder circuit.

Claims (1)

[Scope of Claims] 1. A rotatable head drum that is provided in relation to the position where the magnetic tape wound on the supply reel is transferred to the take-up reel; a first head for recording on a magnetic tape or reproducing a video signal recorded on a magnetic tape; a second head mounted on the head drum so as to have an azimuth different from that of the first head; track identification signal supply means for applying track identification signals of different frequencies between adjacent tracks of the magnetic tape to the second head for recording during recording on the magnetic tape; A magnetic recording/reproducing apparatus comprising: a control means for controlling the relative positional relationship between the magnetic tape and the second head to be changed based on the magnitude of the track identification signal for each frequency. 2. The track identification signal supply means includes at least three signal sources that generate track identification signals of different frequencies, and switches the signal sources each time the position of the track of the magnetic tape with respect to the first head changes. 2. The magnetic recording and reproducing apparatus according to claim 1, further comprising switching means for sequentially applying the output of each signal source to said second head. 3. The control means includes: a tape running drive means for running the magnetic tape and changing the running speed of the magnetic tape; and acting on the tape running drive means based on the frequency of the track identification information. 2. The magnetic recording and reproducing apparatus according to claim 1, further comprising means for changing the running speed of said magnetic tape.